Eyles Nick. Disaster in Japan: What does it mean to us?

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The Sendai earthquake of March 11, 2011: What does it mean to us?

Japan is one of the most dangerous places

to live anywhere on earth: ‘earthquake

central’ with volcanoes thrown in for good

measure. It lies where four plates come

together; and they don’t like each other.

In a relatively small, densely urbanized

island such as this, the effects of

earthquakes, volcanic eruptions and

tsunamis are magnified. Acceptance

ofnatural disasters and the tough times

that follow is hard-wired into the national

psyche.

Japan is made up of some 3,900 islands and four large ones: Honshu; Hokkaido; Kyushu

and Shikoku. Japan was not always surrounded by water but was joined to the Asian

continent until just 15 million years ago. Subduction of the thick oceanic crust of the Pacific

and Philippine plates down below Asia created an arc of volcanoes along the coast

something like the modern day Andes in South America. Old heavy slabs of oceanic crust

such as these descend very steeply under Japan (called a ‘subduction zone’) often curling

under themselves (a process called ‘subduction rollback’). This has had the effect of pulling

off a sliver of continental crust from the outer edge of the Asian continent and opening up

the Sea of Japan (which geologists call a ‘backarc basin’) between the coast and the modern

day islands of Japan.

According to legend, Japan lies above a giant catfish pinned below a granite stone held in

place by a god (Kashima) of the Earth. The thrashing of its tail is felt as an earthquake. The

subducting Pacific plate sticks to the plate above bending its outer edge downward like a

bent ruler. Every now and again, the bending plate (the ruler) springs back violently. Minor

earthquakes are felt almost daily in different parts of the country with some estimates of as

many as 1,200 earthquakes each year; any of these would be of major concern here in

Ontario.

Japan is cut up by major fault zones that divide the country into crustal blocks that mark

the boundaries of the four tectonic plates that make up this part of the Pacific Rim. The

Median Tectonic Line (MTL) is the longest (1,000 km) and divides Japan into a northern

Prof. Nick Eyles by the Chikyu ship

zone made of old continental crust rifted from Eurasia (‘basement rocks’) and a southern

much younger belt of highly deformed rocks scraped of the subducting Pacific Plate together

with volcanic rocks belonging to several arcs. In the east, the Tanakura Tectonic Line (TTL)

separates basement rocks belonging to northeastern Japan from those in the southwest.

The Itoigawa-Shizuoka Tectonic Line (ISTL) cuts Japan completely in half in central Honshu

marking the western side of a broad depression (the Fossa Magna) along the boundary

between the Eurasian and the North American plates.

The Pacific coast of Japan is a long and very dangerous subduction zone. It is made up of

two parts; the Nankai-Suruga Trough south of Tokyo and the Japan Trench to the north.

The Nankai-Suruga Trough marks where low-angle thrust faults dip gently down below

Japan as the Philippine oceanic plate slips under the Asian continental plate. To the north,

the Japan Trench marks where the oceanic Pacific plate dives below North America. Along

the Sagami Trough, the Philippine plate dives down below North America. As a consequence

Tokyo lies at the intersection of the Nankai and Sagami troughs doubling its exposure to

major earthquakes.

The pattern of past earthquakes reveals sectors each with its own clockwork frequency of

tremors. On average, there is a disastrous earthquake every 90 to 150 years. These are

named after the area in which they occur (e.g., the ‘Tonankai Earthquakes’ of 1498, 1605,

1707, 1854 and 1944). This behaviour reflects the ‘stick-slip’ motions of the faults. When

plates are locked, strain builds up and there are no earthquakes (creating what is called a

‘seismic gap’). With time, the strength of rocks is overcome and the fault abruptly ruptures

(slip) creating a powerful tremor, extensive damage and uplift of the coastal margin as the

overlying plate springs free.

In 2009, I met teary survivors of the 1944

Tonankai Earthquake (M7.9) spoke of their

experiences as young school children. They

had gone home for lunch only for the

earthquake to strike leaving many friends dead

under the rubble of their school. Today they

are resigned to another large earthquake in

the near future.

The October 28, 1891 the Nobi Earthquake (M8; also called the Mino-Owari Earthquake)

along the boundary between Eurasian and North American plate (the Itoigawa-Shizuoka

School kids practice emergency drills

Tectonic Line) had a profound psychological effect on Japanese society quite apart from the

physical damage it caused. There was in effect, a crisis of faith. The Meiji Restoration in

1868 led to a rejection of the old Shogun warlord class and the adoption of a more outward

looking approach that embraced western culture and technology. After 1870, foreign

scientists such as British and American engineers were brought to Japan to modernize the

country using steel, concrete and brick in favor of wood which was always susceptible to

fire. The 1891 earthquake revealed the fatal weakness of this approach as steel railway

bridges and western-designed buildings especially factories, collapsed wholesale while

traditional wooden structures swayed but survived. The survival of old wood framed castles

with their tiered structure was highlighted; did they not resemble that most sacred and

most stable edifice Mount Fuji? The striking differences in the effects of the earthquake on

different buildings was to eventually bring about a rejection of western learning, now seen

as weak and vulnerable, in favor of traditional Japanese culture and workmanship.

Henceforth Japan was increasingly wary of western culture, which it saw as inherently weak,

and like its buildings, easily toppled. It’s not a long stretch from the Nobi Earthquake of

1891 to the attack on Pearl Harbor in 1941 as we shall show below.

A segment of the dangerous Neodani Fault

which slipped during the 1891 earthquake

is exposed to view today in the

‘Earthquake Observation Museum’ in

Motosu City in Gifu Prefecture. The

museum is a memorial to the 7000 people

killed when the city of Gifu was completely

leveled. A deep excavation below the

museum’s basement exposes the fault

which cuts through Jurassic sedimentary

rock and basalt. It is a left lateral fault

and moved laterally by 8 m and vertically

by 6 m producing a dramatic fault scarp

still clearly visible outside in the surrounding valley. This earthquake was the subject of a

novel report by John Milne and W.K. Burton (‘The Great Earthquake of Japan 1891’) in

which it was clearly demonstrated (for the first time anywhere) that earthquakes were the

product of slip along faults. They showed too, how the landscape could be read as a record

of past earthquake activity in the form of scarps and offset rivers. It was truly ground

shaking stuff; Milne and Burton later wrote (in 1898) ‘Earthquakes and Other Earth

Prof. Nick Eyles at the Earthquake Observation

Museum

Movements’ where they established the science of seismology and a global monitoring

system for measuring earthquakes. They also developed new instruments (seismographs)

for measuring the size of earthquake waves and use the telegraph system to collect data

from around the world.

Modern earthquakes in Japan are recorded and reported (somewhat strangely at first

glance) by the Japanese Meteorological Association, a throwback to much earlier ideas of

why earthquakes happen. Earth was seen a pan over a fire deep below. Wind, water and fire

were the main earth elements; if the wind blew strongly, the fire would grow, the water

would boil and its lid would bang up and down creating a tremor.

It was a common belief. Shakespeare wrote in King Henry IV;

‘In strange eruptions, oft the teeming earth

Is with a kind of colick pinch'd and vex'd

By the imprisoning of unruly wind

Within her womb; which, for enlargement striving, Shakes the old beldame earth, and

topples down steeples and moss-grown towers.’

Fusakichi Omori (1868-1923) was the first professional Japanese seismologist and

completed a detailed statistical study of weather patterns and air pressure during

earthquakes. He showed that many had occurred at times of little or no wind. In 1899, John

Milne (the father of seismology) wrote a large review article in Nature making reference to

meteorological explanations. In the late nineteenth century, it made perfect sense to place

Japanese seismometers right next to meteorological recording stations.

As head of the Imperial Earthquake Investigation Committee, Omori oversaw the mapping

of damage zones from which earthquake epicentres and the size of the tremors could be

identified. He developed recording instruments (the ‘Omori seismograph’) and mapped

epicentres around the world; his map of Pacific earthquakes identifying distinct ‘zones’

(what was later to be called the ‘Pacific Rim of Fire’) was later used as a key piece of

evidence in the discovery of tectonic plates in the 1960’s. He was the first foreign scientist

to visit San Francisco after the earthquake in 1906, and Messina in Sicily, Italy which killed

120,000 people in 1908 (Europe’s deadliest) and to make detailed reports of the damage.

He showed one again, that masonry and brick buildings were unsuited to earthquake prone

areas.

Omori is perhaps best remembered for his ‘gap theory.’ By mapping the location and timing

of past events, the frequency of major earthquakes would be revealed, giving potentially

life-saving clues as to future events. In this he was absolutely right. He identified ‘seismic

gaps’ where earthquakes were overdue and could be expected shortly; the basis of most

modern predictive capability albeit on timescales of decades not years. But there was a

deadly limitation; Japan is an island and many faults lie offshore out of the reach of

investigation. The great city of Tokyo lies at the head of Sagami Bay and a significant gap

had already been identified as early as 1905 but evidence of past activity lay hidden under

Tokyo Bay. Omori ironically read a series of ‘semi-destructive’ earthquakes in 1922 and

early 1923 as evidence that the gap had been filled. In this opinion, he was catastrophically

wrong. Near noon on September 1, 1923 disaster struck; the Great Kanto earthquake broke

water pipes in Tokyo and 140,000 people died in the earthquake and fire that followed.

Omori was in Australia at the time, returned ill and died in the turmoil just weeks after the

earthquake. Not a fitting end to a fine earthquake scientist.

Frank Lloyd Wright made much of the fact that his Imperial Hotel survived the Great Kanto

Earthquake but there was no escaping the wider message that Japanese-designed buildings

had fared much better. Successive deadly earthquakes had important political consequences

in Japan. Governments were judged by their ability to respond and manage. Central control

was strengthened. Japan defeated a major European power (Russia) in battle in 1905. The

rejection of foreign influences was to eventually push the country into isolation from the

West down the road to military conflict with the West in WWII.

Such is the power of earthquakes.

Prior to this month’s cataclysmic events, the Great Hanshin earthquake of January 17, 1995

was the latest blow to Japan occurring near the city of Kobe. It was the largest ‘quake since

1923. Neither the city nor disaster preparedness managers were fully up to the task of

fighting more than 160 fires. Some 5,000 people died and 300,000 were made homeless.

The epicenter lay southwest of the city and the fault ruptured northwards hurling its force

towards and not away from the city; a process called ‘directivity’ by geologists. Much of the

port city was affected by severe ground shaking in which wet sediments suddenly liquefied

and lost their strength. Infrastructure was not destroyed but rendered useless by tilting and

flooding as the land suddenly sank. In this case, traditional Japanese wood frame houses

with heavy tile roofs were especially at risk when they were shaken.

The lesson here is that every earthquake is different offering new challenges largely

because of the vagaries of local geology below the city and the depth of the quake. At the

time, it was the most expensive natural disaster in history ($100 billion). The Sendai quake

of March 11 will be remembered for its effects on two nuclear plants in Fukushima,

specifically the loss of coolant to keep the reactors cool. The reactors had been shut down

but the backup power supply (diesel generators) failed. At this point (13 March) mildly

radioactive steam has been vented and the status of the plants is uncertain. Japan

generates 30% of its power from nuclear stations that are all at risk in future ‘quakes.

The future is not pleasant

There is a deadly frequency to the

timing of large earthquakes in the

Tokyo area; 1633, 1703, 1872, 1853

and 1923, so the city is overdue for

the next ‘big one’. It got badly

shaken in March 11 but the epicentre

of that quake lay 240 km north and

80 km offshore. Today, some 23

million people live and work in the

greater Tokyo-Yokohama area right

above the convergence of the great

four tectonic plates (Eurasian, North

American, Philippine and Pacific). The

last great earthquake of 1923 on September 1 (the Great Kantō earthquake; M 8.3)

devastated Tokyo and the sister port city of Yokohama. Landslides and fires killed many.

Rumors that Koreans were taking advantage of the earthquake to loot stores lead to a

bloody pogrom. Ever since, the Japanese have emphasized the importance of

communication; giving the public accurate information in the aftermath of an earthquake.

The next large earthquake in Tokyo is expected to create $380 billion of damage and will be

the world’s most expensive catastrophe. Much of Tokyo, like Kobe, is built on wet soft

sediment which can be expected to turn to quicksand. Though new buildings are considered

to be earthquake resistant their design is largely untested and much old housing remains.

Even if the building remains intact, it may well sink into soft sediment below softened by

liquefaction.’ Local geological conditions always dictate the effects of earthquakes; a large

Tokyo prepares for disasters with pre-coordinated

rescue drills

tremor in one area underlain by hard rock can have very different consequences from

another of the same magnitude where soft sediment predominates.

Thanks to the development of plate tectonic theory in the 1960’s, geologists now have a

clear understanding of the causes of earthquakes. But there are still a lot of unanswered

questions surrounding large magnitude ‘super quakes’ triggered in subduction zones. The

ability to predict them is no closer than it was in Omori’s day. Scientists know why these

earthquakes happen, they’re less sure of the precise processes and still can’t yet read the

tell tale signs that precede them.

Offshore, in the Nankai Trough just off

Tokyo, one of the most earthquake prone

regions around the entire Pacific Rim,

scientists on board the Drill Ship ‘Chikyu’

are drilling kilometres into the ocean bed

to reveal the processes at work. They are

looking for clues in the deep sea sediments

being forced down into the subduction

zone and the mechanisms that generate

large earthquakes along these megathrust

faults. The Chikyu (meaning ‘the Earth’) is

a Japanese-built ship capable of drilling to

7,000m below the sea floor to collect rock

samples and install sensors. It employs

state-of-the-art ‘riser’ drilling technology which means that it pumps heavy mud down the

hole to cool the drill bit and can safeguard against dangerous blowouts where rocks contain

gases under very high pressure. An enormous ‘blow-out preventer’ sits on the sea floor.

Formerly gas rich zones were extremely hazardous to earlier generations of drill ships such

as the Canadian-built Resolution. The Chikyu is leased to the Integrated Ocean Drilling

Program (IODP) supported by some 20 countries including Canada.

In late 2009, the Chikyu drilled 2 km deep into the floor of the Nankai Trough located off

the southwest coast of Japan. It is one of the most active earthquake zones on the planet

and the purpose of the drilling expedition is to establish what type of sediments are being

dragged down into the Nankai Trough subduction zone. Previous work suggests the critical

importance of fluids carried down within wet muddy sediments in lubricating slip between

the descending plate and the overriding plate. Monitoring real time fluid pressures are a key

Scientists on board the Drill Ship ‘Chikyu’ are

drilling kilometres into the ocean bed to reveal

the processes at work

objective because higher than usual fluid pressures might mean slippage is imminent thus

foretelling a major, damaging earthquake. Here is a possible key to earthquake prediction.

The long term aims of the Chikyu are ambitious; the private company that owns it wants

one day to be able to drill down through the entire thickness of the Earth’s crust and reach

the mantle; the implications for developing new energy sources and mineral deposits are far

reaching to us all. Unfortunately, there is only one such vessel afloat today.

Currently, the Japanese Meteorological Association operates a national earthquake

observation network collecting data from several thousand monitoring instruments operated

by local governments and the National Research Institute for Earth Science and Disaster

Prevention (NIED). These data are transferred to the headquarters of the Earthquake and

Tsunami Observation System (ETOS) on a real-time basis. In the event of an earthquake,

JMA releases information on its hypocenter, magnitude and shaking intensity to local

disaster prevention authorities through dedicated lines, and to the public through local

governments and the media. This information also plays a vital role as a trigger for rescue

and relief operations.

Not surprisingly, Japan’s budget for

natural disaster management is

huge; about 4.5 trillion yen

equivalent to 5% of the entire

national budget. National Disaster

Prevention Day is held every year on

September 1 (commemorating the

1923 Great Kantō Earthquake) when

the military, various government

agencies, schools and businesses

practice co-ordinated rescue drills.

The last great ‘Tokai earthquake’

occurred in 1853 so it is a safe bet

that the port city of Hamamatsu will be badly damaged in the next few years. We visited

Fukuroi Minami Junior High School to see preparations for an impending earthquake. At

precisely 9 am a siren announced a major earthquake and was followed by frenetic activity

as the school was evacuated and soup kitchens and shelters were quickly set up by the

military. Children watched dramatic rescues of dummies trapped in cars and houses buried

under debris.

National Disaster Prevention Day is held every year on

September 1

Just how effective these drills are in helping real people is being tested now. The calm that

Japan has experienced since 1995 ended abruptly on the March 11

Globally, as urban areas morph into supercities so the susceptibility to geologic hazards

increases. Next up on the watch list is Istanbul.

What does it mean to us?

And what you might ask does all this mean for Canada? We are a Pacific Rim country just

like Japan; the tectonic setting of Vancouver is no different from Tokyo but its geology is

even more hazardous. Much of Vancouver, our only major west coast port, sprawls across

soft wet sediment left by ancestral Fraser River. Large submarine landslides on the river’s

offshore delta tell of large pre historic tremors; ‘ghost forests’ of dead trees suddenly

drowned by subsidence during major earthquakes, and sand layers preserved in coastal

marshes keep a record of ancient Pacific tsunamis. Past is prelude; a foretaste of what is to

come.

Southern Ontario on the other hand, occupies a so-called ‘intraplate’ setting, a safe place it

was then thought when our nuclear plants were built decades ago in the absence of any

fundamental knowledge of the faults that lie directly below Pickering or how Canada’s

geology had even been put together. Some geologists speculate that a large break (rift) in

the crust lies below Lake Ontario connected to the dangerous St. Lawrence Rift which

underlies the Ottawa Valley and St. Lawrence River extending as an arm down the Hudson

valley to New York. Moderately large damaging earthquakes occurred in 1732 (Montreal;

M5.8), in 1935 (Timiskaming; M6.2) and in 1944 (Cornwall, Ontario - Massena, New York;

M5.6). The last was Canada’s costliest with considerable impact on urban infrastructure.

Large landslides in the Ottawa Valley and active faults below the floors of lakes in the

northern reaches of the valley again indicate large prehistoric earthquakes. As geologic

research moves forward, so the ‘recurrence time’ of such earthquakes steadily shrinks. A

magnitude 7 earthquake every couple of thousand years is now suggested. But when was

the last? Do we know the full population of faults below our towns and cities? Do we know

enough about how local rocks and sediments behave when shaken?

The answer is that there is no safe place on the planet; we live on the surface of a mobile

crust always on the move. Safeguarding the population from natural hazards is as important

as preventing wars or disease; perhaps even more so since the last 12 months have been

the deadliest yet for earthquakes.

Here then lie challenges to our universities to educate students and the public regarding the

nature of the planet we live on and the tectonic threat. Here lie opportunities for programs

in environmental geoscience to create those scientists on whom our future might depend;

from pollution, depleting resources, to geologic hazards we need to know much more of our

deadly neighbor.